/*
 * Copyright 2012-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.autoconfigureprocessor;

import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.lang.model.element.AnnotationMirror;
import javax.lang.model.element.AnnotationValue;
import javax.lang.model.element.Element;
import javax.lang.model.element.ElementKind;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.TypeElement;
import javax.lang.model.type.DeclaredType;
import javax.lang.model.type.TypeMirror;
import javax.tools.FileObject;
import javax.tools.StandardLocation;

/**
 * Annotation processor to store certain annotations from auto-configuration classes in a
 * property file.
 *
 * @author Madhura Bhave
 * @author Phillip Webb
 */
@SupportedAnnotationTypes(
        {"org.springframework.context.annotation.Configuration", "org.springframework.boot.autoconfigure.condition" +
				".ConditionalOnClass", "org.springframework.boot.autoconfigure.AutoConfigureBefore", "org" +
				".springframework.boot.autoconfigure.AutoConfigureAfter", "org.springframework.boot.autoconfigure" +
				".AutoConfigureOrder"})
public class AutoConfigureAnnotationProcessor extends AbstractProcessor {

    protected static final String PROPERTIES_PATH = "META-INF/" + "spring-autoconfigure-metadata.properties";

    private Map<String, String> annotations;

    private final Properties properties = new Properties();

    public AutoConfigureAnnotationProcessor() {
        Map<String, String> annotations = new LinkedHashMap<String, String>();
        addAnnotations(annotations);
        this.annotations = Collections.unmodifiableMap(annotations);
    }

    protected void addAnnotations(Map<String, String> annotations) {
        annotations.put("Configuration", "org.springframework.context.annotation.Configuration");
        annotations.put("ConditionalOnClass", "org.springframework.boot.autoconfigure.condition.ConditionalOnClass");
        annotations.put("AutoConfigureBefore", "org.springframework.boot.autoconfigure.AutoConfigureBefore");
        annotations.put("AutoConfigureAfter", "org.springframework.boot.autoconfigure.AutoConfigureAfter");
        annotations.put("AutoConfigureOrder", "org.springframework.boot.autoconfigure.AutoConfigureOrder");
    }

    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        for (Map.Entry<String, String> entry : this.annotations.entrySet()) {
            process(roundEnv, entry.getKey(), entry.getValue());
        }
        if (roundEnv.processingOver()) {
            try {
                writeProperties();
            } catch (Exception ex) {
                throw new IllegalStateException("Failed to write metadata", ex);
            }
        }
        return false;
    }

    private void process(RoundEnvironment roundEnv, String propertyKey, String annotationName) {
        TypeElement annotationType = this.processingEnv.getElementUtils().getTypeElement(annotationName);
        if (annotationType != null) {
            for (Element element : roundEnv.getElementsAnnotatedWith(annotationType)) {
                Element enclosingElement = element.getEnclosingElement();
                if (enclosingElement != null && enclosingElement.getKind() == ElementKind.PACKAGE) {
                    processElement(element, propertyKey, annotationName);
                }
            }
        }
    }

    private void processElement(Element element, String propertyKey, String annotationName) {
        try {
            String qualifiedName = getQualifiedName(element);
            AnnotationMirror annotation = getAnnotation(element, annotationName);
            if (qualifiedName != null && annotation != null) {
                List<Object> values = getValues(annotation);
                this.properties.put(qualifiedName + "." + propertyKey, toCommaDelimitedString(values));
                this.properties.put(qualifiedName, "");
            }
        } catch (Exception ex) {
            throw new IllegalStateException("Error processing configuration meta-data on " + element, ex);
        }
    }

    private AnnotationMirror getAnnotation(Element element, String type) {
        if (element != null) {
            for (AnnotationMirror annotation : element.getAnnotationMirrors()) {
                if (type.equals(annotation.getAnnotationType().toString())) {
                    return annotation;
                }
            }
        }
        return null;
    }

    private String toCommaDelimitedString(List<Object> list) {
        StringBuilder result = new StringBuilder();
        for (Object item : list) {
            result.append(result.length() != 0 ? "," : "");
            result.append(item);
        }
        return result.toString();
    }

    @SuppressWarnings("unchecked")
    private List<Object> getValues(AnnotationMirror annotation) {
        List<Object> result = new ArrayList<Object>();
        for (Map.Entry<? extends ExecutableElement, ? extends AnnotationValue> entry : annotation.getElementValues()
                                                                                                 .entrySet()) {
            String attributeName = entry.getKey().getSimpleName().toString();
            if ("name".equals(attributeName) || "value".equals(attributeName)) {
                Object value = entry.getValue().getValue();
                if (value instanceof List) {
                    for (AnnotationValue annotationValue : (List<AnnotationValue>) value) {
                        result.add(annotationValue.getValue());
                    }
                } else {
                    result.add(value);
                }
            }
        }
        return result;
    }

    private String getQualifiedName(Element element) {
        if (element != null) {
            TypeElement enclosingElement = getEnclosingTypeElement(element.asType());
            if (enclosingElement != null) {
                return getQualifiedName(enclosingElement) + "$" + ((DeclaredType) element.asType()).asElement()
                                                                                                   .getSimpleName()
                                                                                                   .toString();
            }
            if (element instanceof TypeElement) {
                return ((TypeElement) element).getQualifiedName().toString();
            }
        }
        return null;
    }

    private TypeElement getEnclosingTypeElement(TypeMirror type) {
        if (type instanceof DeclaredType) {
            DeclaredType declaredType = (DeclaredType) type;
            Element enclosingElement = declaredType.asElement().getEnclosingElement();
            if (enclosingElement != null && enclosingElement instanceof TypeElement) {
                return (TypeElement) enclosingElement;
            }
        }
        return null;
    }

    private void writeProperties() throws IOException {
        if (!this.properties.isEmpty()) {
            FileObject file = this.processingEnv.getFiler()
                                                .createResource(StandardLocation.CLASS_OUTPUT, "", PROPERTIES_PATH);
            OutputStream outputStream = file.openOutputStream();
            try {
                this.properties.store(outputStream, null);
            } finally {
                outputStream.close();
            }
        }
    }

}
